5-Lipoxygenase (5-LO), an enzyme found in activated mast cells, eosinophils and other leukocytes within the lungs of asthmatic patients, plays an important role in the development of airway inflammation, mucus secretion and increased bronchomotor tone through the synthesis of leukotrienes. The mechanisms responsible for the regulation of 5-LO expression in these cells during differentiation and cytokine activation are manifold and poorly understood. Multiple levels of control appear to be involved and include alterations in gene transcription, RNA translation, enzyme translocation, enzyme inactivation and substrate availability. Recent studies suggest that among these regulatory mechanisms the transcriptional regulation of the 5-LO gene is important and has potential clinical relevance. We have recently identified naturally occurring mutations within the core promoter of the 5-LO gene that alter transcription factor binding and promoter reporter activity. These mutations are unique in that they result in the addition of one, or deletion of one or two, Sp1/Egr-1 consensus binding sites. It has been shown by others that during leukocyte differentiation Sp1 and Egr-1 levels increase significantly; we propose that thee increased levels are responsible for the enhanced levels of 5-LO which are known to be present in mature leukocytes. In patients with asthma mature leukocytes are exposed to a unique inflammatory micro-environment which modifies leukocyte function, yet the effect of inflammatory cytokines on the levels of these transcription factors in leukocytes, and their role in regulating 5-LO expression has not yet been determined. A major goal of our research proposal will be to explore the functional significance of Sp1 and Egr-1 as possible mediators of cytokine-induced 5-LO gene expression in leukocytes. In addition to Sp1 and Egr-1, we have also identified several inducible nuclear proteins that interact specifically with the 5-LO promoter region containing the mutations. Attempts to identify these proteins by supershift analysis have been unsuccessful, suggesting that they may be unique DNA-binding proteins. The second major goal of this research proposal will be to purify and molecularly clone these candidate transcription factors and examine their trans- activating potential, cytokine inducibility and tissue distribution. To accomplish these goals, the Respiratory Division, Department of Medicine and the Vascular Division, Department of Pathology will continue their collaborative efforts. This is an ideal career development project for Dr. Eric Silverman who is a pulmonologist with an interest in gene transcription and a member of both Divisions.